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Vol. xvi. — AUGUST, 1882. — No. 8.
ON THE COMPASS PLANT.
BY BENJAMIN ALVOKD.
SINCE the publication of my paper on the compass plant,
Silpliium laciniatum (see page 12 of " Proceedings of Ameri-
can Association for Advancement of Science at Cambridge, Mass.,
in August, 1849"), I have made no communication concerning
it to any scientific journal, constantly hoping that my army sta-
tion would bring me where I could make more satisfactory ex-
periments. In the meantime it has been made the topic of sev-
eral papers (about fourteen in all) which will be enumerated at
the end of this article.
The Silpliium laciniatum is a perennial plant of the order Com-
posite ; the first year it bears only radical leaves, the second year
and after, it is a flowering herb with four or five leaves on the
stem ; very rough bristly throughout ; leaves pinnately parted,
petioled but clasping at the base. Root very thick. Flowers
yellow. Found on rich prairies of the Mississippi valley from
Minnesota to Texas, not found on the Pacific slope. Stem stout,
irom three to five feet high; leaves ovate in general outline, from
twelve to thirty inches long.
It was first seen by me in the autumn of 1839, on the rich
prairies near Fort Wayne in the north-eastern portion of the
Cherokee nation, near the Arkansas line. I felt assured that its
curious properties had not been made known, to the scientific
world, and after I had explored all those regions on horseback,
and satisfied myself of the verity of the peculiarity, I made it
known to the National Institute in Washington, the officers of
the army having been requested by that enlightened Secretary of
War, Joel R. Poinsett, to aid that society as opportunity should
VOL. XVI. — NO. VIII. 42
On the Compass Plant.
offer. The first communication was dated August 9, 1842, when
I delivered in person to the Secretary of the Institute, Francis
Markoe, Jr., a dried specimen of the plant. My second letter,
published, like the first, in the Proceedings of the Institute, was
dated January 25, 1843.
My principal object now is to record the various experiments
which have, from time to time and in different places, been made
by me or under my direction, to demonstrate that the meridional
position of the plane of the leaf is due to the action of light.
Sitphiiim laciniatum, or Compass Plant of the Western prairies. Radical leaf from
twelve to thirty inches in height.
The property is best exhibited in the radical leaf, which pre-
sents its faces to the rising and setting sun. The flowering plant
also exhibits the property, though imperfectly, but its leaves take
a medium position between their normal and symmetrical arrange,
ment in reference to the stalk, and the tendency to point toward
the north. But I have been not a little surprised to find the
figures of the plant, as given by A. W. B. (Professor A. W. Ben-
net) in Nature, Feb. 1, 1877, and by Sir Joseph D. Hooker in the
London Botanical Magazine for January, 1 881, present not the
i882.] On the Compass Plant. 627
radical leaf, but the flowering plant. The reader of those jour-
nals will look in vain at the drawings to comprehend the polarity
of the plant.
The experiments to which I refer were made on the radical
leaves, which grow to the height of from one to two feet, and are
strong and robust, and not easily disturbed by winds or other
extraneous objects, and therefore the more useful as a guide on
These experiments have been made since my paper was read
in 1849 to the American Association. By them I became satis-
fied that Dr. Gray was right, in 1849, in attributing the pecu-
liarity to the action of light.
1st. — I applied a very delicate galvanometer to the points of
the leaves, so delicate that it should have detected the minutest
quantity of magnetic or galvanic action, and no deflection was
2d. — Powerful magnets did not appear to deflect the leaves.
3d. — The plant was grown in a box, and after the leaves pre-
sented their edges north and south, the box was turned ninety
degrees, and in a few days the leaves were seen to struggle to
get back to their former meridional position.
4th. — Neither J. W. Bailey, LL.D., professor of chemistry at
West Point, nor Professor John Torrey, at Princeton, after careful
analysis in 1842, could detect any traces of the magnetic oxide
of iron in the plant, or iron in any shape.
Mr. Edward Burgess, by request of Professor Asa Gray at
Cambridge, about 1 870, examined with a microscope the two sur-
faces of the leaf of the S. laciniatum, and found the structure of
the epidermal tissue of the two surfaces to be similar, and also
the number of stomata in each face to be about equal. Leaves
generally turn toward the light, and the under surface in such
cases is more " copiously furnished with stomata, or breathing
pores as they are often inaccurately termed, which serve to pro-
mote a diffusion of gases between the external air and the inter-
cellular cavities within the tissue, and especially an abundant
exhalation of aqueous vapor" (W. F. Whitney in American
Naturalist for March, 1871).
My theory is this: all leaves will turn their upper faces toward
the light. But in the compass plant (I speak now of the radical
leaf) the stem comes up vertically and stiffly from the root.
628 On the Compass Plant. [August,
Compelled to move on a vertical axis, the leaf can have no upper
and no lower face, and thus as they struggle toward the light
they face the rising and the setting sun for a position of stable
equilibrium. This is facilitated by the number of stomata on each
face being equal. If the glare of mid-day should attract one
face toward the south, with plane of the leaf east and west, it
would be a position of unstable equilibrium. Some of the ob-
servers have, in rare instances, found exceptions in which this
last named posture of the leaf was found. 1 But it could not
remain long in that situation ; once diverted, it would settle
finally into the meridional position as that of stable equilibrium.
This action of light in its full effect is of course best exhibited on
the open prairies, where both faces would have the equal light of
the sun during the day.
But in the case of the plants grown by Dr. Gray in his botani-
cal garden at Cambridge, they are near houses and trees, and not
in a position assimilated to their native region on the prairies.
Their failure to show the property was a fact stated by Dr, Gray
in 1849 before the American Association when my paper was
read, and it was the cause of his contradiction of the existence of
the property in the edition of his " Botany of the Northern U. S.
for 1846." Down to the present day these plants in his garden
do not show the peculiarity, evidently because they do not, as on
the prairies, have the equal light of the sun during the morning
and the afternoon.
Thus I was fully prepared to expect the result of the experi-
ment by Stahl in Germany, referred to in the number for Febru-
ary, 1882, of the American Journal of Science. It was per-
formed not on the Silphium laciniatum, but on the Lactuca scariola,
and it is but just to Dr. George Engelmann, of St. Louis, to say,
that he made known the existence of polarity in that plant in
August, 1878, to the American Association at St. Louis, also in
the number of the Gardeners' Chronicle, London, for 26th Febru-
ary, 1 88 1.
Stahl states that he " took two plants of the Lactuca scariola
growing in pots and placed one where it would be exposed to
direct sunlight from 10 until 3, and kept in the dark for the rest
1 1 recommend to observers in Minnesota and Wisconsin to see if the exceptions,
when the plant is east and west, are more numerous there than in Arkansas and
Texas, where the sun at noon is higher than in more northern latitudes. The lower
the sun at noon the greater the disturbing effect.
1 882.] On the Compass Plant. 629
of the clay; the other was placed so that from sunrise until 10
o'clock, and from 3 o'clock until sunset, it was exposed to the
sunlight, but from 10 to 3 was in the dark. In the first case the
leaves did not assume a meridional position, but in the second
they did. All this shows that the meridional position is produced
by the sun when near the horizon."
To this can be added that Dr. Engelmann, in a letter to me of
28th Feb., 1882, as also in his article in the Gardeners' Chronicle,
above mentioned, adds that observations with a microscope show
that the number of stomata on the two faces is equal, thus
" showing a similar anatomical structure " to that of the Silphium
The compass plant shows its peculiarity best in mid-summer,
when the plant is in full growth prior to the changes which the
approach of autumn makes in most plants. It is also best shown
in the little hollows on the prairies, where the radical leaves are
somewhat sheltered from the winds, and where they will be seen
all parallel to each other. There are also great varieties in the
size and growth of the S. laciniatuni, both in the radical leaf and
in the flowering plant. I have myself seen the polarity exhibited
in a much more marked manner in some regions than in others.
In this respect in Iowa it was never so apparent as on the prairies
in Missouri, Arkansas and the Cherokee nation.
And I was pleased to hear from Dr. Gray that Sir Joseph
Hooker saw it in Southwestern Missouri, and in mid-summer.
On reaching Boston in 1877, Dr. Gray says, that one of the
first requests of that distinguished botanist was to be shown the
compass plant, and Dr. Gray took him to that region. So that
in the Botanical Magazine for January, 188 1 , he says:
" I have not been able to detect any orientation of the leaves
in the Kew cultivated specimens, but these not being planted in
a good exposure all round, are out of court as witnesses. On the
other hand, when traveling on the prairies with Dr. Gray in 1877,
I watched the position of the leaves of many hundred plants from
the window of the railroad car, and after some time persuaded
myself that the younger, more erect leaves esoecially, had their
faces parallel approximately to the meridian line."
Dr. Gray in the same article (as quoted by Sir Joseph Hooker)
says : " But repeated observations upon the prairies with measure-
ments by the compass 1 of directions assumed by hundreds of
1 In the remarks which followed my piper read in August, 1849, to the Am.
Assoc, (see page 18 of Proceedings), Professor R. Morris said: "In surveying on
630 On the Compass Plant. [August,
leaves, especially of the radical ones, have shown that as to prev-
alent position, the popular belief has a certain foundation in fact."
I wish now to refer to the exceptions. Besides the fact above
stated, that great differences are shown in the growth of the
plant in different states and regions, it has repeatedly been
reported to me that an east and west position of the leaf has
been discovered. In 1843 letters to the National Institute made
the statement that occasionally a leaf would be found east and
west. In a letter to me from St. Louis county, Mo., June 19th,
1866, from Mr. A. Fendler (a very careful painstaking botanist),
he said : " Of the thirty-four leaves examined on the hill, eleven
were in the true meridian, one was due east and west, one was as
much' as 6o° east, and but three deviating more than 25 from
the true meridian. The ' compass plant,' although its leaves do
not invariably point due north and south, is yet entitled to the
name it bears, not only from observations made on the open
prairies, but even from those made on the hills. For in the latter
case I find that about one-third of the number of. their leaves
exactly coincide with the meridian, and more than another third
is of so small an angle as 3 — io° from the true north."
Professor Gray, in the article in the Botanical Magazine above
referred to, says : " As to their orientation, 2 not only is this rather
vague in the cultivated plant, but subject to one singular anom-
aly. I have several times met with a leaf abruptly and perma-
nently twisted to a right angle in the middle, so that while the
the prairies for several years, I have observed that in running compass lines north
and south, the edge of the leaf was seen, so that the plant was not at all conspicu-
ous; but in running lines east and west, the whole plant was seen, and it was a very
conspicuous object." The Rev. Thomas Hill, LL.D., then president of Harvard
Univ., in the number of American Journal of Science fox Nov., 1863, communicated
the result of cxreful observations on the prairies near Chicago, with compass in
hand, on the 8th of August. He appears to have examined the flowering plant, not
the radical leaf. He speaks of twenty-nine plants which bore ninety-one leaves.
He says the average of sixty-nine leaves was "about half a degree east of the mer-
idian," and that twenty-five were less than i°. If the flowering plant would give
such results, the average of radical leaves would have been still more satisfactory.
He has a paper on the same subject in Americam Naturalist for 1870.
2 The word "orientation" is, I find, used by some scientists to describe north and
south position, but it is ambiguous, for the compass plant faces the west as much as
the east. It was called, when I first saw it, the " polar plant " by the officers of the
army and the frontiersmen. But the name of " compass plant " is much better, as
the other name might be mistaken as referring to some plant near the polar regions.
If I use the word "polarity" in this paper it is only in the sense of its tendency to
assume the meridional position.
1 882.] On the Compass Plant. 631
lobes of the basal half pointed say east and west, those of the
apical half pointed north and south."
My explanation of the east and west position observed by Mr.
Fendler is, that while under the action of light the situation of
the leaf for a position of stable equilibrium, is to face the rising
and setting sun, it might, under the glare of the mid-day sun
have temporarily, as a position of unstable equilibrium, taken a
posture east and west. This would be when the whole leaf faces
toward the south. But the anomaly of " an abrupt torsion of
90 in the middle of the blade" (again referred to by Dr. Gray in
reference to Professor Farlow's note on Stahl),.is one for future
observers to scan, who live near the plant on the prairies. If the
basal half was not from any cause free to change its direction, the
phenomenon would appear to be explained.
Now as to other plants, reports, after my first communication
to the National Institute in 1842, were received from the West
by that society, stating that other plants on the prairies were
found to possess the same peculiarity. My paper of August,
1849, sa 'd : " Proper observation and experiments may discover
traces of some general law for these results." We have men-
tioned above the experiment on the Lactnca scariola. All tends
to confirm the idea that the polarity is due to the action of light.
Besides that plant, Stahl names Aplopappus rubiginosus, Lac-
tnca saligna, and Chrondrella juncea, and he " believes that many
other examples will be found, especially among the plants of dry
and exposed regions."
I have now to add that observations made during the last
twelve months on the Chinese arbor-vitae, or Thuja orientalis, in
this city (Washington), convince me that when raised in a hedge
only three or four years old and three or four feet high, its
broad leaves will face the rising and setting sun. In the court-
yard of Professor C. V. Riley, corner of 13th and R streets, N.
W., there are two such hedges of the plants ; one running east
and west, the other north and south. Both exhibited the prop-
erty. In reference to the former hedge running east and west, if
it might be supposed that the pointing north of the leaves well in
view, might be due to the other leaves, except at the ends, being
hidden from view, interlocked by the closeness of the hedge, I
answer: look at the other hedge running north and south, and
the verity of the meridional position of the leaves is there
632 On the Compass Plant. [August,
also clearly apparent. Dr. J. G. Hunt, of Philadelphia, a distin-
guished microscopist, examined some of the leaves of the Thuja
orientalis which I sent him, and says, June 19, 1881, that "there
is no structural difference in the two sides' of the leaves on the
plant." It is only in the young plant three or four feet high that
this is seen, for in the beautiful clumps of the Thuja orientalis
eight to twelve feet high, the leaves, all vertical, radiate in every
direction from the trunk of the tree.
A friend from Louisiana, the late Professor C. G. Forshey,
wrote me that he had formed the same conclusion concerning
this plant as to its meridional position under certain circum-
Mr. William Saunders, superintendent of the garden at the
Agricultural Department in this city, informs me that the leaves
of the Eucalyptus polyanthemus are vertical and have the number
of stomata the same on both faces. But confined in a conserva-
tory nothing is known of any tendency of the leaves to face the
rising and setting sun.
If it is asked why I was at an early date disposed to look to
other agencies than light as possibly concerned in causing the
peculiarity of the compass plant, I answer that I was fresh from
the study of electro-magnetism. Read section 105 of Roget's
Electro-magnetism on the electrical spiral coil (the " Solenoid "),
by which currents of electricity cause it to act when suspended
on a vertical axis, like the magnet in pointing to the north. Read
the treatises on vegetable physiology which speak of the spiral
coils in the leaves of various plants, and " that one of the most
remarkable properties of vegetable membrane is its power of
allowing fluids to pass slowly through it, even though no visible
pores or apertures can be detected in it." " The spiral filaments
are found in leaf-stalks from which their spiral fibers can be un-
coiled." Thus ii experiment and dissection of the compass
plant could in any way favor the idea of such anatomical struc-
ture, its polarity might be sought for in electric currents. To
this day the best received theory of the magnetism of the earth
is Ampere's, that it is due to electric currents from west to east
around the crust of the globe ; and that a steel magnet is caused
by electric currents transverse to its axis and permeating its
But when one agency is sufficient to account for the phenome-
1 882.] On the Compass Plant. 633
non, it is unnecessary to search for another. And this brings me
to refer to the admirable drawing of the transverse section of the
leaf, magnified 235 times, of Silphium laciniatnm, given on page
157 of Botany by C. E. Bessey, professor of botany in the Iowa
Agricultural College. He says, " Its chlorophyll-bearing paren-
chyma is almost entirely arranged as palisade tissue, so that the
upper and lower portions are almost exactly identical in struc-
ture ;" on page 103 he says, " there are in the true upper surface
52,700 stomata per square inch, and on the under surface 57,300
per square inch."
This magnifying of a section of the leaf is a dissection, and
thus there is no cause to suppose the existence of any spiral
ducts such as are above referred to. Professor Bessey, living in
the prairie region has the best possible opportunities to observe
the compass plant. He says, page 515: "Its large pinnately
lobed leaves twist upon their petioles, so as to present one surface
of the blade to the east and the other to the west, the two edges
being upon the meridian." This language applies to the leaves
of the flowering plant, for in the growing of the radical leaf there
is no cause for the twisting of the petiole- in order that it may
assume its meridional position.
As to the history of the plant in Europe. The following is an
extract from the article by Sir Joseph Hooker in the London
Botanical Magazine for January, 18S1, above quoted, which is
preceded by a drawing of the flowering plant :
"This noble plant was introduced into Europe in 1781 by
Thouin and flowered for the first time in the Botanical Garden
of Upsala in Sweden. It has been in cultivation in Europe ever
since, though its name and fame as the compass plant of the
prairies are of comparatively modern date, it having before that
borne the popular names of turpentine plant and rosin weed, ex-
cept among the hunters and settlers in the Western States. With
regard to the history of its reputed properties as an indicator of
the meridian by the position of its leaves, I am fortunate in hav-
ing recourse to my friend Professor Asa Gray, now in England,
who has most kindly furnished me the following very interesting
account of this matter:
'" The first announcement of the tendency of the leaves of the
compass plant to direct their edges to the north and south, was
made by General (then Lieutenant) Alvord of the U. S. Army, in
the year 1842, and again in 1849, in communications to the Amer-
ican Association for the Advancement of Science. But the fact
appears to have long been familiar to the hunters who traversed
634 On the Compass Plant. [August,
the prairies in which this plant abounds. The account was some-
what discredited at the time by the observation that the plants
cultivated in the Botanical Garden at Cambridge, U. S., did not
distinctly exhibit this tendency.'" 1
Nature for Feb. 1, 1877, contains the first of a series of articles
by " A. W. B." on " Remarkable Plants," and begins with the
compass plant as No. I. It says: "Our illustration is taken
partly froai the plate in Jacquin's ' Eclogae,' the only good draw-
ing of the plant published, assisted by comparison with dried
specimens in the Kew Plerbarium." The full title 2 of Jacquin's
book, published in Latin in Vienna in, 1812, is, " Selections of
rare and little-known plants, described from living plants with col-
ored illustrations." Like the plant in Upsala, Sweden, in 178 1, it
was cultivated, but its true rarity, and its claims for interest and
investigation, were quite unknown.
If it is asked what remains for the observation of scientists in
this connection, we answer, that besides the occasional torsion of
90° referred to by Dr. Gray, and the exceptions to the rule in
which the whole leaf is east and west, to which we have briefly
alluded, we will add : the whole subject of the reason (the entire
rationale) of leaves turning towards the light is worthy of more
full experiment and elucidation.
I had written the above sentence when I was pleased to see in
the American Journal of Science for March, 1882, a communica-
tion by Dr. Asa Gray, stating the substance of a paper by Fran-
cis Darwin, in Journal of the Linnaean Society, 188 1, "On the
power possessed by leaves of placing themselves at right angles
to the direction of incident light." Dr. Gray concludes his
abstract by saying : "The experiments varied in many ways, and
with arrangements to eliminate epinastic and hyponastic ten-
1 Dr. Gray adds: "The lines in 'Evangeline' were inspired by a personal com-
munication made by Gen. Alvord to the poet Longfellow." This was in January,
1847. Sir Joseph Hooker adds in a note after quoting the lines," I cannot congrat-
ulate the poet on the fidelity of the plant as a 'delicate one.' " The same criticism
is made by the article in Nature. The truth is, I wrote Professor Longfellow after
" Evangeline " first came out that the plant was not a " delicate " one, but on the
contrary, stout and robust, and therefore a better image of faith. " Such in the soul
of man is faith," &c, &c, and in all the later editions of " Evangeline," Mr. Long-
fellow calls it a "vigorous plant." But in England the first editions are most read.
2 Eclogpe plantarum rariorum et minus cognitarum, quas ad vivum descripsit et
iconibus coloratis illustravit. Fehr. Jos. Fry. Jacquin. Fasc. I-x. Fol maj. Wien,
1 882.] On the Compass Plant. 635
dencies, plainly bring out the conclusion ' that the power which
leaves have of placing themselves at right angles to the incident
light is due to a specialized sensitiveness to light, which is able
to regulate or govern the action of other external forces, such
Professor Bessey, in his recent admirable work on botany, page
193, says: "The explanation for heliotropism which is com-
monly given, is that the light retards the growth on the illumi-
nated side, while the shaded side elongates, resulting in a tension
which necessarily produces a curvature."
This is the most plausible statement we have seen, but we are
not informed how far it is founded on any actual experiment. It
is satisfactory that Mr. Darwin has undertaken the task in such a
careful and systematic manner. It is an interesting field of ob-
servation and worthy of being thoroughly examined by different
persons and in different localities.
LIST OF PAPERS ON THE COMPASS PLANT, ETC.
Benjamin Alvord, U. S. Army. — Proceedings of National Institute, Washington,
D. C, 1842 and 1843.
Proceedings of American Association for the Advancement of Science (page
12) at Cambridge, Mass., August, 1849.
Thomas Hill, LL.D. — American Journal of Science for November, 1863, p. 439.
American Naturalist, 1870, p. 495.
J. A. Allen. — American Naturalist, 1870, p. 5S0.
W. F. Whitney. — American Naturalist for March, 1871, p. 1.
Professor Alfred W. Bennett, Lecturer on Botany at St. Thomas Hospital,
Eng. — Nature for Feb. 1, 1877, p. 298, with figure of the plant.
Dr. George Engelmann, of St. Louis. — American Association for Advancement
of Science, St. Louis, Aug., 1878.
Professor C. E. Bessey. — American Naturalist for August, 1877, p. 4S6.
Botany. Henry Holt & Co., N. Y., 1880, pages 103, 157, 515, with figures of
section of leaf magnified.
Dr. Asa Gray.— Ed. of 1S80 of Botany of Northern U. S.
American Journal of Science for March, 1882, page 245. On Francis Dar-
win's paper in Journal of the Linntean Society, No. 112, Vol. iS, pp. 42c-
455> J une 1881, on " The power possessed by leaves of placing themselves at
right angles to the direction of incident light."
Sir Joseph D. Hooker and Dr. Asa Gray. — London Botanical Magazine for Jan-
uary, 1 88 1.
Gardeners' Chronicle, p. 276, for Feb. 26, 1881.
" W. G. F.," or Professor W. G. Farlow, of Hirvard University. — American
Journal of Science for February, 1882, p. 157, giving extracts from Stahl in
the Jen. Zeitschrift, Germany.